The present invention relates generally to hearing systems and, more particularly, to a hearing system that relies on electromagnetic fields to produce vibrations on a portion of the human ear. Such systems may be used to enhance the hearing of persons with normal or impaired hearing.
Hearing systems which rely on amplified acoustic drive output are well known in the prior art. For example, public address (PA) systems used in auditoriums or concert halls provide sounds to an audience with normal hearing by widespread production of amplified acoustic information in the form of sound waves. Such systems, however, are incapable of selectively imparting audio information to some nearby individuals but not to others. If amplification of such systems is increased so as to enable hearing impaired individuals to receive the information, the volume may be too loud for persons with normal hearing.
Another type of acoustic drive sound system is exemplified by the commonly available acoustic hearing aid. Such devices rely on acoustic output provided by a miniature speaker typically located within the wearer's ear canal, and positioned adjacent to the ear drum. In many cases, a portion of the acoustic output feeds back to the input of the device, causing a self-sustained oscillation. This "feedback" phenomenon, which is generally proportional to the magnitude of the gain, imposes limitations on the amount of gain available to the wearer. As a result, many hearing impaired individuals cannot benefit from such devices. This is especially true for severely hearing impaired individuals, where high acoustic gain requirements result in unacceptable levels of acoustic feedback.
Some prior art hearing systems have utilized electromagnetic energy to vibrate the middle ear structures or the tympanic membrane. An example of this may be found in U.S. Pat. No. 4,957,478 to Maniglia. The Maniglia system uses a hearing device consisting of a microphone, an amplifier, a power source, and an electromagnetic coil placed in the external auditory canal for receiving sound waves and converting them into magnetic fields. A permanent magnet is surgically implanted onto a portion of the bones of the ossicular chain of the individual. The magnet responds to the applied magnetic field, and causes the bones of the ossicular chain to vibrate with the same frequency and amplitude variation as the incoming signal at the microphone. In an alternate embodiment, a radio frequency (RF) signal is externally modulated by a sound signal. The resulting signal is then transmitted through an external coil worn behind the ear to a coil implanted in the mastoid cavity. The mastoid cavity coil decodes the signal to retrieve the original signal, which is then applied to a third coil which vibrates the implanted magnet, resulting in the perception of sound. In the above cases, as well as others not mentioned here, a considerable amount of conspicuous hardware is required for the system to operate. Additional disadvantages include surgical intervention with its various associated risks.
Another type of system proposed by the prior art (Rutschmann, 1959; Goode, 1973) utilizes a small magnet glued or otherwise attached to the tympanic membrane. A coil placed inside or just outside the external auditory canal is driven by currents to produce electromagnetic fields which vibrate the magnet attached to the tympanic membrane. In the case of the Rutschmann system, the current requirement was impractically high for hearing threshholds. The Goode system, on the other hand, provided some improvements in terms of power consumption, but the requirements were still impractically high. Power consumption and other limitations related to coil and magnet design made it necessary, in those systems, to place the coils in close proximity to the magnet.
It is therefore an object of the present invention to provide an improved hearing system.
Another object of the invention is to provide an improved hearing system which is capable of vibrating a magnet subjected to electromagnetic fields produced by a coil which is positioned outside of the ear canal of an individual.
Another object of the invention is to provide an improved hearing system which is capable of conveying information to an individual in a completely inconspicuous way.
It is a further object of the invention to provide an improved hearing system which is capable of conveying audio information to an individual in a manner which is selective to the wearer and substantially unaffected by ambient sound.
Still another object of the invention is to provide an improved hearing system for transmitting audio information to an individual.
Other objects of the invention will become apparent to those skilled in the art from the following description and accompanying drawings.